MEAM势与Tersoff势比较研究——碳化硅熔化与凝固行为

运用分子动力学方法对比模拟研究了碳化硅的体熔化、表面熔化和晶体生长过程.分别采用MEAM 势和Tersoff势两种势函数描述碳化硅.结果表明:体熔化时,两种势函数描述的SiC的原子平均能量、 Lindemann指数和结构有序参数与温度的变化关系相似,但MEAM势对应的体熔点(4250 K)比Tersoff势(4750 K) 的要高.表面熔化时,两种势函数描述的SiC在相同的过热度下熔化速度相近;而在相同的温度条件下,MEAM 作用的SiC表面熔化速度更快.这是由于MEAM势SiC的热力学熔点(3338 K)低于Tersoff势SiC的热力学熔点 (3430 K)的缘故.两种势函数作用的SiC在晶体生长方面差异很大.MEAM势SiC的晶体生长速度与过冷度有关, 过冷度约为400 K时晶体生长速度最快.但Tersoff势SiC晶体却在过冷度为0—1000 K的范围内均不能生长. 综合考虑,MEAM势比Tersoff势能更好地描述碳化硅的熔化和凝固行为.

A comparative study between MEAM and Tersoff potentials on the characteristics of melting and solidification of carborundum

Molecular dynamic simulations of bulk melting,surface melting and crystal growth of SiC are carried out.The atomic interactions in SiC are calculated by MEAM and Tersoff potentials separately.The results show that the bulk melting of SiC with MEAM potential exhibits its relations to temperature similar to that with Tersoff potential,while can be indicated by the mean atomic energy,Lindemann index and structure order parameter.The difference between them is the bulk melt point:MEAM is 4250 K,while Tersoff is 4750 K. At the same superheat degree,the velocities of surface melting of SiC separately,with MEAM and Tersoff potentials are in substantial agreement.But at the same absolute temperature,the surface melting of SiC with MEAM potential is faster than that which the Tersoff potential,which is due to the difference in thermodynamic melting point.The Measured value of the thermodynamic melting point of MEAM is 3338 K compared with 3430 K of Tersoff.On the crystal growth side,the crystal growth velocity of SiC with MEAM potential is related to the undercooling.The fastest velocity corresponds to the undercooling of 400 K.However,the crystal of SiC with Tersoff potential cannot grow in the undercooling of 0 K—1000 K.Overall,the MEAM potential is better than Tersoff potential in the sense of describing the melting and solidification of carborundum.